He will be tested Friday morning at 11, an examination the Red Sox hope will give clearer answers about his condition - and might help them decide whether they must consider putting him on the disabled list.

Ellsbury was out of Boston's lineup against Kansas City. The Red Sox don't know the problem.

"We've got to get to the bottom of this. We're not at the bottom of it," manager Terry Francona said.

"We don't want to rush into putting him on the DL, and at the same time, he's not ready to play because of the way he feels.''

Ellsbury has said the pain is near the four ribs he cracked in an April 11 collision.

More than a week passed before the Red Sox diagnosed that the ribs were cracked.

The new flareup affects his back ribs as well, he said. There is no progress, only a concern the situation might worsen.

"It's the same. Not better,'' Francona said after Thursday night's 4-3 loss to Kansas City.

After Wednesday's game at Tampa Bay, Ellsbury expressed dissatisfaction with the way the injury has been handled from the start, when it was diagnosed as bruised ribs.

"They said you treat it all the same way,'' he told ESPN.com.

"Remember that comment? How do you treat a bruise the same as a break?''